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Fuel gauge probems still
https://www.ausmini.com/forums/viewtopic.php?f=2&t=95634		 Page 1 of 1
Author:  cooperized [ Sun Jun 25, 2017 1:04 pm ]
Post subject:  Fuel gauge probems still
Previously I posted a post about Fuel gauge decreasing at higher revs. I have made up a new voltage regulator using an IC voltage regulator, it is controlling at 10 volts. I have run another earth lead from the speedo to the body. I have earthed the return wire at the sender- the gauge goes to full. When I rev the car when it is parked the gauge acts as expected. It is only when I drive it does the gauge to 1/2 full from full. I may have to take it to an auto electrician as I am stumped as to what the problem maybe.

Cheers' Scott.
Author:  gtogreen1969 [ Sun Jun 25, 2017 1:45 pm ]
Post subject:  Re: Fuel gauge probems still
Is the back of the speedo open to the engine bay? Airflow has been known to effect gauges.
viewtopic.php?t=91462
Author:  drmini in aust [ Sun Jun 25, 2017 3:08 pm ]
Post subject:  Re: Fuel gauge probems still
Have you removed the sender and checked it's resistance from full to empty positions? With wear the wiper arm can get loose against the resistor winding.
Author:  cooperized [ Sun Jun 25, 2017 6:56 pm ]
Post subject:  Re: Fuel gauge probems still
The speedo is not open to air flow. I haven't had the sender out because it seems to work, because it is ok at idle. When I rev the car when it is standing still the gauge stays where it should, only goes to half when I drive it.
Author:  8700s14 [ Sun Jun 25, 2017 7:50 pm ]
Post subject:  Re: Fuel gauge probems still
I am no expert, but I would imagine the motion of the car actually moving is enough to upset the sender unit.
Author:  cooperized [ Sun Jun 25, 2017 8:06 pm ]
Post subject:  Re: Fuel gauge probems still
I will purchase a new sender as I am at my wits end to what the problem is. Thanks for all the comments.
Author:  simon k [ Mon Jun 26, 2017 3:25 pm ]
Post subject:  Re: Fuel gauge probems still
lol - my car does the same - went through the same, voltage reg, airflow, earthing, different gauge etc. etc. I still think airflow is the cause, as per the thread Dr Mini linked above...

phillb wrote:
Mick wrote:
I hadn't sealed up the adjustment holes on the back of my gauges, and found the breeze pushing through from the engine bay via the gauge was cooling the bimettallic heated strip down. This made both the temp gauge AND the fuel gauge drop as speed picked up. I hadn't considered this before, but noticed that air whistled through my gauge bezels as I drove along... (This only affects the very slow moving gauges as opposed to later magnetic gauges by the way)


I discovered that if I wound down my drivers window (esp in winter) the gauges dropped, wind it up and the gauges rose. This was even with the adj. holes covered. Same reason, ....more wind drew past the gauges with the window down.

They can be very sensitive but very accurate when supplied with a steady voltage and calibrated correctly.



I just ignore it. I usually know how much fuel the car has in it. If I stop and it's below the E mark, I find a servo and put some in.

Does your temp gauge do the same thing? It used to do it for my temp gauge too, but when I injected the car I needed a different type of sender so I made a servo driven gauge
Author:  cooperized [ Mon Jun 26, 2017 8:26 pm ]
Post subject:  Re: Fuel gauge probems still
Thanks Simon for the reply.

yes my temperature gauge does the same thing. I have the MK2/MIni k setup. I have the mat which has sponge on the back of it with vinyl on top of it which covers the firewall speedo area. I thought this would stop airflow around the speedo area- maybe not?. I mention the problem to an auto electrician today and he said it was an odd one which he could not give a solution to.
Author:  cooperized [ Mon Jun 26, 2017 8:39 pm ]
Post subject:  Re: Fuel gauge probems still
One thing I forgot to mention was that I did notice was I took a resistance measurement between the back of the speedo and the body with the engine off and it was approx. 6 ohms. I ten started the engine 2000 rpm and te resistance was a lot higher. That is when I added another earth lead- I thought it may have fixed the problem, but it didn't. My blinkers seem to be flashing faster though.
Author:  simon k [ Mon Jun 26, 2017 9:13 pm ]
Post subject:  Re: Fuel gauge probems still
cooperized wrote:
I took a resistance measurement between the back of the speedo and the body with the engine off and it was approx. 6 ohms. I ten started the engine 2000 rpm and te resistance was a lot higher.


there's gotta be something in that... what about at 4000rpm? what about testing how much current flows from the regulator to the temp gauge at RPM steps... ?

cooperized wrote:
That is when I added another earth lead


did you remove the old earth lead? shouldn't make a difference (path of least resistance) but it's possible to get a loop going.

the back of a mini engine bay does get a lot of air pressure going, so any way for air to get from there to behind the speedo housing will be taken... I wonder what would happen if you put the temp gauge in a plastic bag and hung it out of the speedo housing so there was no chance of air rushing past it
Author:  cooperized [ Mon Jun 26, 2017 9:59 pm ]
Post subject:  Re: Fuel gauge probems still
No I didn't remove the earth. Its part of the loom and screws on the back of the speedo where the regulator bolts to. I ran another wire from there to the body. More investigative work required.
Author:  simon k [ Mon Jun 26, 2017 10:04 pm ]
Post subject:  Re: Fuel gauge probems still
cooperized wrote:
No I didn't remove the earth. Its part of the loom and screws on the back of the speedo where the regulator bolts to. I ran another wire from there to the body. More investigative work required.


keep me posted ;)
Author:  9YaTaH [ Tue Jun 27, 2017 7:13 am ]
Post subject:  Re: Fuel gauge probems still
cooperized wrote:
No I didn't remove the earth. Its part of the loom and screws on the back of the speedo where the regulator bolts to. I ran another wire from there to the body. More investigative work required.


Careful you don't introduce an earth loop with unintended consequences :idea: :D
Author:  phillb [ Tue Jun 27, 2017 10:08 am ]
Post subject:  Re: Fuel gauge probems still
cooperized wrote:
Thanks Simon for the reply.

yes my temperature gauge does the same thing. I have the MK2/MIni k setup. I have the mat which has sponge on the back of it with vinyl on top of it which covers the firewall speedo area. I thought this would stop airflow around the speedo area- maybe not?. I mention the problem to an auto electrician today and he said it was an odd one which he could not give a solution to.


Just something simple to try which helped mine. Cut a square of underfelt and fit/tuck it in the hole behind the speedo then the firewall blanket over that. That was me with the gauge that reacted to window up or down.

I reckon though it's a loose connection somewhere or a fault made worse with vibration.


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